Non-vertical through-via in package

ABSTRACT

A package includes a device die, a through-via having a sand timer profile, and a molding material molding the device die and the through-via therein, wherein a top surface of the molding material is substantially level with a top surface of the device die. A dielectric layer overlaps the molding material and the device die. A plurality of redistribution lines (RDLs) extends into the dielectric layer to electrically couple to the device die and the through-via.

BACKGROUND

With the evolving of semiconductor technologies, semiconductorchips/dies are becoming increasingly smaller. In the meantime, morefunctions need to be integrated into the semiconductor dies.Accordingly, the semiconductor dies need to have increasingly greaternumbers of I/O pads packed into smaller areas, and the density of theI/O pads rises quickly over time. As a result, the packaging of thesemiconductor dies becomes more difficult, which adversely affects theyield of the packaging.

Conventional package technologies can be divided into two categories. Inthe first category, dies on a wafer are packaged before they are sawed.This packaging technology has some advantageous features, such as agreater throughput and a lower cost. Further, less underfill or moldingcompound is needed. However, this packaging technology also suffers fromdrawbacks. Since the sizes of the dies are becoming increasinglysmaller, and the respective packages can only be fan-in type packages,in which the I/O pads of each die are limited to a region directly overthe surface of the respective die. With the limited areas of the dies,the number of the I/O pads is limited due to the limitation of the pitchof the I/O pads. If the pitch of the pads is to be decreased, solderbridges may occur. Additionally, under the fixed ball-size requirement,solder balls must have a certain size, which in turn limits the numberof solder balls that can be packed on the surface of a die.

In the other category of packaging, dies are sawed from wafers beforethey are packaged. An advantageous feature of this packaging technologyis the possibility of forming fan-out packages, which means the I/O padson a die can be redistributed to a greater area than the die, and hencethe number of I/O pads packed on the surfaces of the dies can beincreased. Another advantageous feature of this packaging technology isthat “known-good-dies” are packaged, and defective dies are discarded,and hence cost and effort are not wasted on the defective dies.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIGS. 1 through 17 illustrate the cross-sectional views of intermediatestages in the packaging of a device die in accordance with someembodiments, with the respective through-vias having a sand timerprofile;

FIGS. 18 through 21 illustrate the cross-sectional views of intermediatestages in the packaging of a device die in accordance with someembodiments, with the respective through-vias having a mushroom shape;

FIGS. 22 through 29 illustrate the cross-sectional views of intermediatestages in the packaging of a device die in accordance with someembodiments, with the respective through-vias having tapered upperparts; and

FIG. 30 illustrates a process flow for forming a package in accordancewith some embodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the invention. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. For example, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed between the first and second features, such thatthe first and second features may not be in direct contact. In addition,the present disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed.

Further, spatially relative terms, such as “underlying,” “below,”“lower,” “overlying,” “upper” and the like, may be used herein for easeof description to describe one element or feature's relationship toanother element(s) or feature(s) as illustrated in the figures. Thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. The apparatus may be otherwiseoriented (rotated 90 degrees or at other orientations) and the spatiallyrelative descriptors used herein may likewise be interpretedaccordingly.

A package and the method of forming the same are provided in accordancewith various exemplary embodiments. The intermediate stages of formingthe package are illustrated. The variations of the embodiments arediscussed. Throughout the various views and illustrative embodiments,like reference numbers are used to designate like elements.

FIGS. 1 through 17 illustrate the cross-sectional views of intermediatestages in the formation a package in accordance with some embodiments.The steps shown in FIG. 1 through 17 are also illustrated schematicallyin the process flow 300 shown in FIG. 30. In the subsequent discussion,the process steps shown in FIGS. 1 through 17 are discussed referring tothe process steps in FIG. 30.

FIG. 1 illustrates carrier 20 and release layer 22 disposed on carrier20. Carrier 20 may be a glass carrier, a ceramic carrier, or the like.Carrier 20 may have a round top-view shape and may have a size of asilicon wafer. For example, carrier 20 may have an 8-inch diameter, a 12inch diameter, or the like. Release layer 22 may be formed of apolymer-based material (such as a Light To Heat Conversion (LTHC)material), which may be removed along with carrier 20 from the overlyingstructures that will be formed in subsequent steps. In some embodiments,release layer 22 is formed of an epoxy-based thermal-release material.In other embodiments, release layer 22 is formed of an ultra-violet (UV)glue. Release layer 22 may be dispensed as a liquid and cured. Inalternative embodiments, release layer 22 is a laminate film and islaminated onto carrier 20. The top surface of release layer 22 isleveled and has a high degree of co-planarity.

Dielectric layer 24 is formed on release layer 22. In accordance withsome embodiments of the present disclosure, dielectric layer 24 isformed of a polymer, which may also be a photo-sensitive material suchas polybenzoxazole (PBO), polyimide, or the like, that may be easilypatterned using a photo lithography process. In alternative embodiments,dielectric layer 24 is formed of a nitride such as silicon nitride, anoxide such as silicon oxide, PhosphoSilicate Glass (PSG), BoroSilicateGlass (BSG), Boron-doped PhosphoSilicate Glass (BPSG), or the like.

Referring to FIG. 2, Redistribution Lines (RDLs) 26 are formed overdielectric layer 24. The respective step is shown as step 310 in theprocess flow shown in FIG. 30. RDLs 26 are also referred to as backsideRDLs since they are located on the backside of device die 36 (FIG. 8).The formation of RDLs 26 may include forming a seed layer (not shown)over dielectric layer 24, forming a patterned mask (not shown) such as aphoto resist over the seed layer, and then performing a metal plating onthe exposed seed layer. The patterned mask is then removed, followed bythe removal of the seed layer previously covered by the removedpatterned mask, leaving RDLs 26 as in FIG. 2. In accordance with someembodiments, the seed layer comprises a titanium layer and a copperlayer over the titanium layer. The seed layer may be formed using, forexample, Physical Vapor Deposition (PVD). The plating may be performedusing, for example, electroless plating.

Referring to FIG. 3, dielectric layer 28 is formed on RDLs 26. Thebottom surface of dielectric layer 28 is in contact with the topsurfaces of RDLs 26 and dielectric layer 24. In accordance with someembodiments of the present disclosure, dielectric layer 28 is formed ofa polymer, which may be a photo-sensitive polymer such as PBO,polyimide, or the like. In alternative embodiments, dielectric layer 28is formed of a nitride such as silicon nitride, an oxide such as siliconoxide, PSG, BSG, BPSG, or the like. Dielectric layer 28 is thenpatterned to form openings 29 therein. Hence, RDLs 26 are exposedthrough the openings 29 in dielectric layer 28.

FIGS. 4 through 7 illustrate the formation of metal posts 38. Throughoutthe description, metal posts 38 are alternatively referred to asthrough-vias 38 since metal posts 38 penetrate through the subsequentlyformed molding material. The respective step is shown as step 312 in theprocess flow shown in FIG. 30. Referring to FIG. 4, metal seed layer 30is formed, for example, through Physical Vapor Deposition (PVD). Metalseed layer 30 may include copper, and may include a titanium layer and acopper layer over the titanium layer in accordance with someembodiments. Photo resist 32 is formed over metal seed layer 30. Inaccordance with some embodiments, photo resist 32 is a dry film, whichis laminated onto metal seed layer 30. In alternative embodiments, photoresist 32 is formed by spin coating.

A light-exposure is then performed on photo resist 32 using a photolithography mask (not shown), which includes transparent portionsallowing light to pass through and opaque portions for blocking thelike. After the development, openings 34 are formed in photo resist 32,as shown in FIG. 5. Metal seed layer 30 is exposed to openings 34.Openings 34 have a sand timer profile, with the bottom width W1 and topwidth W2 being greater than middle width W3. Furthermore, the smallestwidths of openings 34 may be close to the middle heights of openings 34.

The material of photo resist 32 is selected to make the resultingopenings 34 to have the sand timer profile. In some exemplaryembodiments, the photo resist includes TOK P50 series photo resist(manufactured by Tokyo Ohka Kogyo America Incorporated). The TOK P50 mayinclude polyacrylate, cross-linker, and photo-sensitive initiator insome embodiments. With the proper photo resist material being used, andprocess conditions for exposing and development being tuned, the sandtimer profile may be generated.

Next, as shown in FIG. 6, through-vias 38 are formed by plating. Theplating rate is controlled to ensure that the shape of the platedthrough-vias 38 follow the shape of openings 34. In subsequent steps,photo resist 32 is removed, and hence the underlying portions of metalseed layer 30 are exposed. The exposed portions of metal seed layer 30are then removed in an etching step. The resulting through-vias 38 areillustrated in FIG. 7. Throughout the description, the remainingportions of metal seed layer 30 are also referred to as parts ofthrough-vias 38.

Through-vias 38 have the shape of rods, with the middle portions beingnarrower than the respective top portions and the respective bottomportions. It is noted that FIG. 7 illustrates the shapes of through-vias38 in one vertical plane. If viewed from any other vertical plane,through-vias 38 may also have the sand timer profile. The top-viewshapes of through-vias 38 may be circles, rectangles, squares, hexagons,or the like.

FIG. 8 illustrates the placement of device die 36. The respective stepis shown as step 314 in the process flow shown in FIG. 30. It isappreciated that although a single device die 36 is illustrated, aplurality of device dies identical to device die 36 will also be placedover dielectric layer 28 during this step. Device die 36 is adhered todielectric layer 28 through Die-Attach Film (DAF) 45, which may be anadhesive film. Device die 36 may be a logic device die including logictransistors therein. In some exemplary embodiments, device die 36 isdesigned for mobile applications and may be a Power ManagementIntegrated Circuit (PMIC) die, a Transceiver (TRX) die, or the like.

In some exemplary embodiments, metal pillars 50 (such as copper posts)are pre-formed as the topmost portions of device die 36, and metalpillars 50 are electrically coupled to the integrated circuit devicessuch as transistors in device die 36. In accordance with someembodiments of the present disclosure, a polymer fills the gaps betweenneighboring metal pillars 50 to form top dielectric layer 47. Topdielectric layer 47 may be formed of PBO in accordance with someexemplary embodiments. In accordance with some embodiments, the topsurface of top dielectric layer 47 is higher than the top surface ofmetal pillars 50.

Next, as shown in FIG. 9, molding material 44 is molded on device die36. The respective step is shown as step 316 in the process flow shownin FIG. 30. Molding material 44 fills the gaps between neighboringthrough-vias 38 and the gaps between through-vias 38 and device die 36.Molding material 44 may include a molding compound, a molding underfill,an epoxy, or a resin. The top surface of molding material 44 may behigher than the top ends of through-vias 38 and metal pillars 50.

Further referring to FIG. 10, a planarization such as a ChemicalMechanical Polish (CMP) step or a grinding step is performed to thinmolding material 44, until through-vias 38 and metal pillars 50 areexposed. The respective step is shown as step 318 in the process flowshown in FIG. 30. Due to the planarization, the top ends of through-vias38 are substantially level (coplanar) with the top surfaces of metalpillars 50, and are substantially coplanar with the top surface ofmolding material 44.

FIGS. 11 through 15 illustrate the formation of front side RDLs. Therespective step is shown as step 320 in the process flow shown in FIG.30. Referring to FIG. 11, dielectric layer 52 is formed. In someembodiments, dielectric layer 52 is formed of a polymer such as PBO,polyimide, or the like. In alternative embodiments, dielectric layer 52is formed of silicon nitride, silicon oxide, or the like. Openings 53are formed in dielectric layer 52 to expose through-vias 38 and metalpillars 50. The formation of openings 53 may be performed through aphoto lithography process.

Next, referring to FIG. 12, Redistribution Lines (RDLs) 54 are formed toconnect to metal pillars 50 and through-vias 38. RDLs 54 may alsointerconnect metal pillars 50 and through-vias 38. RDLs 54 include metaltraces (metal lines) over dielectric layer 52 as well as vias extendinginto the openings in dielectric layer 52 to electrically connect tothrough-vias 38 and metal pillars 50. RDLs 54 are formed in a platingprocess, wherein each of RDLs 54 includes a seed layer (not shown) and aplated metallic material over the seed layer. The seed layer and theplated material may be formed of the same material or differentmaterials. RDLs 54 may comprise a metal or a metal alloy includingaluminum, copper, tungsten, and alloys thereof. RDLs 54 are formed ofnon-solder materials. The via portions of RDLs 54 may be in physicalcontact with the top surfaces of metal pillars 50.

Referring to FIG. 13, dielectric layer 56 is formed over RDLs 54 anddielectric layer 52. Dielectric layer 56 may be formed using a polymer,which may be selected from the same candidate materials as those ofdielectric layer 52. For example, dielectric layer 56 may comprise PBO,polyimide, BCB, or the like. Alternatively, dielectric layer 56 mayinclude non-organic dielectric materials such as silicon oxide, siliconnitride, silicon carbide, silicon oxynitride, or the like. Openings 59are also formed in dielectric layer 56 to expose RDLs 54. The formationof openings 59 may include a photo lithography process.

FIG. 14 illustrates the formation of RDLs 58, which are electricallyconnected to RDLs 54. The formation of RDLs 58 may adopt similar methodsand materials to those for forming RDLs 54. RDLs 58 and 54 are alsoreferred to as front-side RDLs since they are located on the front sideof device die 36.

As shown in FIG. 15, an additional dielectric layer 62, which may be apolymer layer, is formed to cover RDLs 58 and dielectric layer 56.Dielectric layer 62 may be selected from the same candidate polymersused for forming dielectric layers 52 and 56. Opening(s) 63 are thenformed in dielectric layer 62 to expose the metal pad portions of RDLs58.

FIG. 16 illustrates the formation of Under-Bump Metallurgies (UBMs) 64and electrical connectors 66 in accordance with some exemplaryembodiments. The respective step is shown as step 322 in the processflow shown in FIG. 30. The formation of UBMs 64 may include depositionand patterning. The formation of electrical connectors 66 may includeplacing solder balls on the exposed portions of UBMs 64 and thenreflowing the solder balls. In alternative embodiments, the formation ofelectrical connectors 66 includes performing a plating step to formsolder regions over RDLs 58 and then reflowing the solder regions.Electrical connectors 66 may also include metal pillars or metal pillarsand solder caps, which may also be formed through plating. Throughoutthe description, the combined structure including device die 36,through-vias 38, molding material 44, and the corresponding RDLs anddielectric layers will be referred to as package 100, which may be acomposite wafer with a round top-view shape.

Next, package 100 is de-bonded from carrier 20. In the de-bonding, atape (not shown) may be adhered onto dielectric layer 62 and electricalconnectors 66. In subsequent steps, light such as UV light or laser isprojected on release layer 22 to decompose release layer 22, and carrier20 and release layer 22 are removed from package 100. A die saw step isperformed to saw package 100 into a plurality of packages, eachincluding a device die identical to device die 36 and the surroundingthrough-vias 38. The respective step is shown as step 324 in the processflow shown in FIG. 30. One of the resulting packages is shown as package102 in FIG. 17.

FIG. 17 illustrates the bonding of package 102 with another package 200.The respective step is shown as step 326 in the process flow shown inFIG. 30. In accordance with some embodiments of the present disclosure,the bonding is performed through solder regions 69, which join the metalpad portions of RDLs 26 to the metal pads in package 200. In someembodiments, package 200 includes device dies 202, which may be memorydies such as Static Random Access Memory (SRAM) dies, Dynamic RandomAccess Memory (DRAM) dies, or the like. The memory dies may also bebonded to package substrate 204 in some exemplary embodiments.

In the resulting package in FIG. 17, through-via 38 has top width W2′,bottom width W1, and smallest width W3′ smaller than both top width W2′and bottom width W1. Width W3′ may be at or close to the middle heightof through-via 38. In accordance with some exemplary embodiments, widthdifference (W1−W3′) is smaller than about 50 μm, and may be greater thanabout 5 μm. Width difference (W2′−W3′) may also be smaller than about 50μm, and may be greater than about 5 μm. In accordance with someembodiments of the present disclosure, from the top to the bottom of athrough-via 38, the widths of the through-via 38 gradually andcontinuously reduce from top width W2′ to smallest width W3′, and thengradually and continuously increase from the smallest width W3′ tobottom width W1. Bottom tilting angle θ1 and top tilting angle θ2 of thesidewalls of through-vias 38 may be smaller than about 88 degrees inaccordance with some embodiments of the present disclosure.

By forming the sand timer profile, the top area of through-via 38 isincreased compared to vertical through-vias. As a result, the interfacearea between through-via 38 and the overlying RDLs 54 and dielectriclayer 52 is also increased. The stress applied on the interface isaccordingly reduced. The likelihood of the cracking of dielectric layer52 and the peeling of dielectric layer 52 from the underlying structuresis thus reduced.

FIGS. 18 through 21 illustrate cross-sectional views of intermediatestages in the formation of a package in accordance with alternativeembodiments. Unless specified otherwise, the materials and the formationmethods of the components in these embodiments are essentially the sameas the like components, which are denoted by like reference numerals inthe embodiments shown in FIGS. 1 through 17. The details regarding theformation process and the materials of the components shown in FIGS. 18through 21 (and FIGS. 22 through 29) may thus be found in the discussionof the embodiments shown in FIGS. 1 through 17.

The initial steps of these embodiments are essentially the same as shownin FIGS. 1 through 5. Next, as shown in FIG. 18, through-vias 38 areplated. The plating is continued until the top surfaces of through-vias38 are level with the top surface of photo resist 32. The plating isfurther continued with an over-plating process, during which thethrough-vias 38 are plated over the top surface of photo resist 32.During the over-plating, through-vias 38 grow horizontally to formthrough-via caps 38A, which are the top portions of through-vias 38. Theresulting through-vias 38 thus have a mushroom profile with caps 38Ahaving widths abruptly greater than the underlying body portions 38B ofthrough-vias 38.

Next, photo resist 32 is removed, and the portions of seed layer 30covered by photo resist 32 are removed through etching. The resultingstructure is shown in FIG. 19. Device die 36 is then placed ondielectric layer 28, as shown in FIG. 20. The subsequent process stepsare essentially the same as shown in FIGS. 9 through 17. The resultingstructure is shown in FIG. 21.

In the planarization step similar to what is shown in FIG. 10, the topportions of through-via caps 38 are removed, and the bottom portions ofthrough-via caps 38 remain. The resulting through-via caps 38A have flattop surfaces level with the top surfaces of molding material 44 andmetal pillars 50. As shown in FIG. 21, through-vias 38 includethrough-via caps 38A and underlying through-via bodies 38B. Inaccordance with some embodiments, through-via bodies 38B have the sandtimer profile similar to that in FIG. 17. The details of the sand timerprofile may be the same as in FIG. 17, and hence are not repeatedherein. Through-via bodies 38B may also have other profiles. Forexample, through-via bodies 38B may have straight sidewalls 38′, asillustrated on one of the illustrated through-vias 38 as an example.Straight sidewalls 38′ may be vertical or substantially vertical, forexample, with the tilting angle being between 89 degrees and about 91degrees.

Through-via body 38B have top width W2′. Through-via cap 38A have bottomwidth W4, wherein the transition from width W2′ to width W4 may beabrupt or gradual. Width W4 is greater than width W2′, and may begreater than all widths of the respective underlying through-via body38B. In accordance with some embodiments, width W4 is in the rangebetween about 40 μm and about 140 μm. Width difference (W4−W2′) may besmaller than about 50 μm, and may also be greater than about 5 μm inaccordance with some embodiments. In some embodiments, width difference(W4−W2′) is in the range between about 10 μm and about 30 μm. ThicknessT1 of through-via caps 38A may be in the range between about 5 μm andabout 10 μm.

In accordance with some embodiments of the present disclosure,through-via caps 38A have planar top surfaces 38T, planar bottomsurfaces 38BT, and curved sidewalls 38S connecting the planar topsurface 38T to the planar bottom surface 38BT.

Advantageously, with the formation of through-via caps 38A, the topareas of through-vias 38 are increased. As a result, the overlay windowis increased, wherein if misalignment occurs in the formation of RDLs54, the via portions of RDLs 54 may still land on through-vias 38. Theseembodiments may be used in fine-pitch through-vias, in whichthrough-vias 38 are thin, and hence the via portions of RDLs 54 are morelikely to be misaligned from through-vias 38. A further advantageousfeature of these embodiments is that the interface area betweenthrough-vias 38 and the overlying RDLs 54 and dielectric layer 52 isalso increased, which results in the reduction in the stress and thelikelihood of delamination between through-vias 38 and the overlyingRDLs and dielectric layer.

FIGS. 22 through 29 illustrate the formation of a package in accordancewith yet alternative embodiments. The initial steps of these embodimentsare shown in FIGS. 1 through 4. Next, as shown in FIGS. 22 and 23, adeeper-focus exposure and a shallower-focus exposure are performed. Thefocus of the deeper-focus exposure is deeper into photo resist 32 thanthe focus of the shallower-focus exposure. In accordance with someembodiments of the present disclosure, the focus of the deeper-focusexposure is at the depth D1 (from the top surface of photo resist 32,not shown). The focus of the shallower-focus exposure is at the depth D2greater than D1. In some embodiments, the first exposure (FIG. 22) isthe deeper-focus exposure, with lithography mask 68 used, and the secondexposure (FIG. 23) is the shallower-focus exposure. In alternativeembodiments, the first exposure (FIG. 22) is the shallower-focusexposure, with lithography mask 68 used, and the second exposure (FIG.23) is the deeper-focus exposure.

After the deeper-focus exposure and the shallower-focus exposure, photoresist 32 is developed to form openings 34, as shown in FIG. 24. Theresulting opening 34 may have a lower portion 34A having substantiallystraight sidewalls 34A′ and upper portion 34B having substantiallystraight sidewalls 34B′, wherein sidewalls 34A′ and the respectiveoverlying sidewalls 34B′ have a distinguishable joint, at which there isa distinguishable reduction in the tilting angle of sidewalls. Thetilting angles of sidewalls 34A′ is θ1, and the tilting angles ofsidewalls 34B′ is θ3, which is smaller than tilting angle θ1. Thedifference (θ1−θ3) may be greater than about 2 degrees. The tiltingangle θ3 of sidewalls 34B′ may be in the range between about 85 andabout 90 degrees in accordance with some embodiments, while tiltingangle θ1 of sidewalls 34A′ may be between about 89 degrees and about 91degrees in some embodiments.

Next, as shown in FIG. 25, through-vias 38 are formed by plating. Photoresist 32 is then removed, and the portions of seed layer 30 covered byphoto resist 32 are removed through etching. The resulting structure isshown in FIG. 26. Device die 36 is then placed on dielectric layer 28,as shown in FIG. 27. Molding material 44 is then applied, and aplanarization is performed, as shown in FIG. 28. The subsequent processsteps are essentially the same as shown in FIGS. 11 through 17. Theresulting structure is shown in FIG. 29.

Referring to FIG. 29, through-vias 38 have lower portions 38C andtapered upper portions 38D, which are formed in opening portions 34A and34B (FIG. 24), respectively. Accordingly, the profiles of lower portions38C and upper portions 38D are the same as the profiles of therespective lower opening portions 34A and upper opening portions 34B. Inaccordance with some embodiments of the present disclosure, bottom widthW1 and top width W2′ of through-vias 38 have difference (W1−W2′), whichis smaller than about 50 μm, and may be greater than about 5 μm. HeightH1 of the tapered upper portion 38D to height H2 of the entirethrough-via 38 have ratio H1/H2, which may be smaller than about 0.4 insome embodiments.

Advantageously, with the tapered upper portions 38D of through-vias 38,by forming tapered upper 4 portions for through-vias, the sheer stressapplied to RDLs by the through-vias is reduced, and the reliability ofthe resulting package is improved.

In accordance with some embodiments of the present disclosure, a packageincludes a device die, a through-via having a sand timer profile, and amolding material molding the device die and the through-via therein,wherein a top surface of the molding material is substantially levelwith a top surface of the device die. A dielectric layer overlaps themolding material and the device die. A plurality of RDLs extends intothe dielectric layer to electrically couple to the device die and thethrough-via.

In accordance with alternative embodiments of the present disclosure, apackage includes a device die, and a through-via including a through-viabody and a through-via cap over and connected to the through-via body.The through-via cap is wider than the through-via body. The packagefurther includes a molding material molding the device die and thethrough-via therein, wherein a top surface of the molding material issubstantially level with a top surface of the device die. A dielectriclayer overlaps the molding material and the device die, with a bottomsurface of the dielectric layer contacting the top surface of the devicedie and the top surface of the molding material. A plurality of RDLsextends into the dielectric layer to electrically couple to the devicedie and the through-via.

In accordance with yet alternative embodiments of the presentdisclosure, a package includes a device die, and a through-via includinga lower portion having a first sidewall with a first tilting angle andan upper portion over and connected to the lower portion. The upperportion has a second sidewall having a second tilting angle smaller thanthe first tilting angle. The package further includes a molding materialmolding the device die and the through-via therein, wherein a topsurface of the molding material is substantially level with a topsurface of the device die. A dielectric layer overlaps the moldingmaterial and the device die. A plurality of RDLs extends into thedielectric layer to electrically couple to the device die and thethrough-via.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A package comprising: a device die; athrough-via, wherein the through-via has a sand timer profile, wherein alongitudinal cross-section profile of the through-via is curvedcontinuously; a molding material molding the device die and thethrough-via therein, wherein a top surface of the molding material issubstantially level with a top surface of the device die; a firstdielectric layer overlapping the molding material and the device die; asecond dielectric layer overlapped by the molding material and thedevice die; a via in the second dielectric layer, wherein the via andthe through-via in combination comprise: a metal seed layer comprising afirst metal, wherein the metal seed layer comprises a first portion as abottom portion of the via, a second portion as a bottom portion of thethrough-via, and a third portion lining a sidewall of the via; and ametallic material comprising a second metal different from the firstmetal; and a plurality of redistribution lines (RDLs) extending into thefirst dielectric layer to electrically couple to the device die and thethrough-via.
 2. The package of claim 1, wherein a bottom surface of thethrough-via is coplanar with a bottom surface of the molding material.3. The package of claim 1, wherein a smallest width of the through-viais at an intermediate height of the through-via, and a top width and abottom width of the through-via are both greater than the smallestwidth.
 4. The package of claim 3, wherein in a longitudinalcross-sectional view of the through-via, the through-via has an uppersidewall higher than the intermediate height, and a lower sidewall lowerthan the intermediate height, and the upper sidewall is joined to thelower sidewall with no abrupt change in tilting angle at a respectivejoint.
 5. The package of claim 3, wherein from a top surface of thethrough-via to the intermediate height of the through-via, widths of thethrough-via continuously and smoothly decrease.
 6. The package of claim3, wherein from the intermediate height of the through-via to a bottomsurface of the through-via, widths of the through-via continuously andsmoothly increase.
 7. The package of claim 1, wherein a top tiltingangle of a sidewall of the through-via is smaller than about 88 degrees.8. A package comprising: a device die; a through-via comprising: athrough-via body; and a through-via cap over and connected to thethrough-via body, wherein an entirety of the through-via body isnarrower than an entirety of the through-via cap, and wherein thethrough-via body and the through-via cap are formed of a same materialwithout distinguishable interface therebetween; a molding materialmolding the device die and the through-via therein, wherein a topsurface of the molding material is substantially level with a topsurface of the device die and a top surface of the through-via cap; adielectric layer overlapping the molding material and the device die;and a plurality of redistribution lines (RDLs) extending into thedielectric layer to electrically couple to the device die and thethrough-via.
 9. The package of claim 8, wherein the through-via cap hasa substantially planar bottom surface.
 10. The package of claim 8,wherein a width of the through-via cap is greater than a top width ofthe through-via body by a difference in a range between about 5 μm andabout 50 μm.
 11. The package of claim 8, wherein the through-via cap hasa planar top surface, and a curved sidewall connecting the planar topsurface to a bottom surface of the through-via cap, with the bottomsurface of the through-via cap being planar, wherein throughout anentirety of the through-via cap, upper portions of the through-via capare increasingly narrower than lower portions of the through-via cap.12. The package of claim 8, wherein the through-via body has a sandtimer profile.
 13. The package of claim 8, wherein the through-via bodyhas straight and substantially vertical sidewalls.
 14. A packagecomprising: a device die; a through-via comprising: a lower portionhaving a first sidewall having a first tilting angle, wherein the firsttilting angle is substantially a right angle, and the lower portion hasa substantially uniform width; and an upper portion over and connectedto the lower portion, wherein the upper portion has a second sidewallhaving a second tilting angle smaller than the first tilting angle,wherein higher portions of the upper portion are increasingly narrowerthan respective lower portions of the upper portion, and the secondsidewall that is tilted is physically joined to the first sidewall thatis straight and vertical; a molding material molding the device die andthe through-via therein, wherein a top surface of the molding materialis substantially level with a top surface of the device die; adielectric layer overlapping the molding material and the device die;and a plurality of redistribution lines (RDLs) extending into thedielectric layer to electrically couple to the device die and thethrough-via.
 15. The package of claim 14 further comprising: anadditional dielectric layer overlapped by the molding material and thedevice die; and a via extending into the additional dielectric layer,wherein the via and the through-via comprise a same metallic material,and have no distinguishable interface therebetween.
 16. The package ofclaim 14, wherein the through-via has a top surface and a bottom surfacecoplanar with the top surface and a bottom surface of the moldingmaterial respectively.
 17. The package of claim 14, wherein a firsttilting angle of the first sidewall is greater than a second tiltingangle of the second sidewall by a difference greater than about 2degrees.
 18. The package of claim 14, wherein the through-via has abottom width and a top width smaller than the bottom width by adifference greater than about 5 μm.
 19. The package of claim 14, whereina ratio of a height of the upper portion of the through-via to a heightof an entirety of the through-via is smaller than about 0.4.
 20. Thepackage of claim 8, wherein sidewalls of the through-via cap have aconvex shape.